The present invention relates, in general, to a continuous wave femtosecond optical parametric oscillator (OPO) having high power, short pulses, and broad tunability. More particularly, the invention is directed to an optical parametric oscillator with enhanced performance which utilizes a KTA nonlinear crystal.
The recent development of externally pumped high-repetition-rate femtosecond (fsec) optical parametric oscillators using KTiOPO.sub.4 (KTP) has demonstrated the feasibility of a broadly tunable high-repetition-rate femtosecond light source. Laser pulses in the femtosecond time domain; i.e., pulses having widths of 10.sup.-15 to 10.sup.-13 seconds, are important tools for use in studying extremely short-variation events such as chemical reactions, for by directing femtosecond pulses at reacting chemicals, for example, researchers can capture spectroscopic information about the structure and behavior of short-lived molecular intermediates of the reactions. Femtosecond lasers are also important for studying the dynamics and the ultimate limits of high-speed semiconductor electronic and optical devices. However, numerous ultrafast phenomena have been inaccessible to direct optical study due to a lack of light sources having appropriate wavelengths or other suitable characteristics such as tunability or a high repetition rate. The potential tuning range of the femtosecond KTP optical parametric oscillator, which is such a high-repetition-rate femtosecond source, is from approximately 0.95 .mu.m to about 4 .mu.m with an absorption band around 3.5 .mu.m, and such a source has been extremely valuable in conducting a variety of optical studies. However, there is a need for a high power source of optical pulses which will not only be tunable, but which will have a range beyond that presently available from currently available KTP optical parametric oscillators, and which will have pulse widths as short as 84 fsec.